In the present work, the excited states (singlet and triplet) for three different porphyrins, with and without coordinated Pt(II) complex derivatives, were investigated by three different temporal laser regimes were employed in the Z-Scan technique. Intersystem crossing time (singlet to triplet conversion mechanism) was obtained by a combination of Z-Scan with single or with a train of picosecond laser pulses. These measurements have shown that the excited state absorption spectrum shows distinct absorption behaviors. Also, the absorption cross-section is equivalent to the ground state, describing no changes in the optical transmittance. Fluorescence lifetimes and quantum yields were determined, respectively, by time resolved fluorescence analysis. To determine the intersystem crossing time constant, two additional levels were incorporated to the rate equation model. Moreover, fluorescence decays, internal conversion and ISC times have shown a strong dependence in Pt(II) derivatives and their position to the porphyrin ring (meta or para position). (C) 2018 Elsevier B.V. All rights reserved.